1. Field of the Invention
The present invention relates in general to couplers, and more particularly, to couplers for coupling pipes which are used in a cooling system of an automotive air conditioner. More specifically, the present invention is concerned with couplers of a type which couple a coolant pipe from an evaporator of a cooler unit with another pipe which leads to a compressor or condenser.
2. Description of the Prior Art
In order to clarify the task of the present invention, the piping of a cooler unit installed in a conventional automotive air conditioner will be outlined with reference to FIGS. 2 and 3 of the accompanying drawings, which piping is shown in, for example, Japanese Utility Model First Provisional Publication No. 63-30210.
Generally designated by numeral 1 in FIG. 2 is a cooler unit of a conventional automotive air conditioner. The unit 1 comprises an evaporator which cools air supplied thereto and two case parts 2 and 2 which are combined to form a housing in which the evaporator is installed. The case parts 2 and 2 both have an inlet opening 3 to which an air intake unit (not shown) is connected and an outlet opening 4 to which a heater unit (not shown) is connected. The air intake unit is the means through which ambient air and passenger room air are forced to flow, and the heater unit has therein a heater which heats the cooled air from the cooler unit to a desired degree before the air is blown into the passenger room.
Designated by numerals 5a and 5b are inlet and outlet pipes for coolant, which have respective end portions projected into the case parts 2 and fixed to inlet and outlet openings of a coolant passage of the evaporator.
Each pipe 5a or 5b is provided at an outside end with an externally threaded coupler 6 to which a pipe (not shown) leading from a compressor or condenser is connected.
The detailed structure of the externally threaded coupler 6 is shown in FIG. 3. FIG. 3 shows a condition wherein the pipe 5a passes through an opening 12 formed in a dash panel 11 of a motor vehicle. As is known, the dash panel 11 is a member by which an engine room "E" and a passenger room "R" is bordered. In order to stably and sealably hold the pipe 5a in the opening 12 of the dash panel 11, a collar 7 made of aluminium or aluminium alloy is employed, which is intimately and tightly disposed about the pipe 5a. A grommet 13 is further employed, which is fixed to the opening 12 and holds the collar 7 in a manner to achieve a watertight sealing therebetween.
Assembly of the collar 7 and the coupler 6 to the pipe 5a is carried out in the following manner.
First, the collar 7 and the coupler 6, in this order, are loosely received onto the outwardly projected end portion of the pipe 5a. Then, with an aid of a holder (not shown), the collar 7 and the coupler 6 are stationally held keeping contact therebetween. Then, by using a reamer 9 as shown in FIG. 4, the end portion of the pipe 5a is enlarged to such a degree that the outer surface thereof frictionally contacts the inner cylindrical surfaces of the coupler 6 and the collar 7. Then, by using another reamer (not shown), the terminal end of the pipe 5a is further enlarged to such a degree that the outer surface thereof frictionally contacts the inner cylindrical surface of an enlarged part of the bore of the coupler 6. With these steps, the coupler 6 and the collar 7 are fixed to the pipe 5a.
As is shown in FIG. 4, the reamer 9 for enlarging the diameter of the pipe 5a (or 5b) comprises a cylindrical rod part (no numeral) and four axially extending ridges 10. The ridges 10 taper toward one end of the rod part.
The pipe 5a thus equipped with the collar 7 and the coupler 6 is then inserted through the grommet 14 which has been fixed to the opening 12 of the dash panel 11, so that the coupler 6 is exposed to the engine room "E".
The grommet 13 has a labyrinth seal 14 integrally formed thereon, which seal sealingly contacts the outer surface of the collar 7. Because of this labyrinth seal 14, watertight sealing is achieved in the opening 12.
However, due to its inherent construction, the above-mentioned coupling structure has the following drawbacks.
First, the manual labor for enlarging the diameter of the pipe 5a by using the reamer 9 is very troublesome thereby deteriorating the manufacturing efficiency of the air conditioner.
Second, the collar 7 is costly because of the thicker construction of the same.
Third, the outlet pipe 5b tends to emit a rasping noise due to the flow of the coolant therethrough. Although this noise may be eliminated when a silencer is fixed to the pipe 5b, the cost of the cooler unit becomes high.